1. Field of the Invention
The present invention relates to a flexible, self-supporting, anti-adhesive and cellular membrane, defining a mould or cavity plate for preparing food products, in particular, but not exclusively, bakery, viennoiserie, pastry and biscuit products, and in particular for moulding, fermenting and baking bread dough.
The invention relates more particularly to improvements made to the membranes of the above-mentioned type that are the subject of the Applicant's patents EP 0 235 037 B1 and FR 2 658 034, and as also described in patent applications FR 2 774 554 and WO 03/066328.
2. Description of the Related Art
EP 0 235 037 B1 discloses an anti-adhesive former or membrane, intended to support pieces of bread dough or similar throughout the process of fermenting and baking the dough, this membrane being constituted by at least one silicone elastomer or a silicone resin associated with a reinforcing web, said membrane being self-supporting, having a general configuration and predetermined dimensions such that it can rest detachably and interchangeably on a single supporting tray, and being preformed so as to have at least one hollow cavity independent of the support and having any desirable shape corresponding to the individual shapes for breadmaking or similar to be subjected to the fermenting and baking process.
Such a membrane, which can support dough pieces not only during the stages of fermenting and baking dough, but also throughout the intermediate handling and storing stages, can either be aerated or not aerated, and can include a woven, knitted or non-woven web, constituted by glass yarns and/or carbon fibres and/or ceramic threads impregnated and/or coated with at least one elastomer or a silicone resin, conferring the desired anti-adhesive properties. Preforming of the membrane is obtained by moulding and/or forming then stiffening by vulcanization of the elastomer(s) or by curing the silicone resin(s).
Thus, a moulded membrane can have an undulating profile in the form of quasi semi-cylindrical depressions that are more or less broad with a more or less flattened base, these depressions being optionally separated by gaps embodied by a flat surface situated at the top of the depressions and providing an improved heat circulation, or having a succession of flat-bottomed rectangular or square spans, separated by a fold in the shape of an inverted V, for receiving pieces of bakery or viennoiserie dough.
In the case of a pressed membrane, the membrane can have, longitudinally and transversally, successions of hollow cavities, having a rectangular or square shape with a clearance allowing the baked pieces to be removed, and separated by narrow strips, or the membrane can be pressed so as to create oblong-shaped oval cradles with a clearance for allowing the pieces to be removed, these cradles succeeding each other in an adjacent fashion, in order to receive pieces such as rolls or croissants, or also the membrane can be pressed so as to create successive lines of round, hollow dishes, having flat bottoms and a variable diameter, depth and clearance, according to the nature of the pieces to be baked, such as round rolls, rolls for hamburgers, muffins, currant buns, or also the membrane can be pressed so as to create a succession of hollow semi-cylinders of varying width and length, for receiving pieces such as hot-dog rolls or fancy shaped baguettes.
In order to support the food products to be processed, at least one membrane as presented above can rest, detachably and interchangeably, on a supporting tray, to which the membrane can optionally be detachably connected, the tray having the shape of a rectangular or square container, with a flat bottom, preferably open-worked, also within side walls serving to keep the preformed membrane in place, these side walls allowing the trays to be piled or stacked, preferably made of metal, or also of a non-dielectric material that can be used in a microwave oven, the tray moreover being capable of being adapted to the sliding fittings of an oven or to a trolley on which the tray is mounted or incorporated, and intended to enter successively into proving cabinets then ventilated ovens, optionally rotating, or tunnel ovens, for example.
The multi-purpose equipment comprising several membranes having varying numbers and/or shapes of cavities and at least one, but preferably several, associated support trays, allows, in particular, intermediate handling to be dispensed with in the case of peel ovens or tunnel ovens, can be used for all types of products prepared, in particular by the baker/confectioner, with the minimum of bulk and immobilization, both in the peel oven and in the ventilated oven, or even in the tunnel ovens of industrial bakeries, whilst any damaged membrane can be easily replaced, without the need for intervention on the other components of this multi-purpose equipment or system.
In fact, this multi-purpose system offers the possibility of using a set of new membranes that are flexible, interchangeable owing to their fully detachable character with respect to the support in the shape of a tray with side walls intended to receive them, preformed according to the dimensions and shapes of all the varieties of breadmaking products, and which therefore has a very high degree of flexibility in use for the traditional or industrial baker, (for all breads and all ovens), and is very economical, owing to the reduced costs and storage requirements, the field of use of this multi-purpose system not being limited to baking and/or confectionery, but extending to related fields such as biscuit products and cold meat products, and any kind of food products, such as quiches, tarts, pies etc., capable of being prepared by private individuals, industry professionals, the restaurant trade, in a traditional manner, on a production line or industrially.
Patent FR 2 658 034 relates to improvements made to the multi-purpose equipment according to EP 0 235 037 B1 and as shown above and intended to be used for deep-freezing and/or baking of viennoiserie, pastries, fermented or not, egg-yolk dough, biscuits, creams or baked custards, or even some small breadmaking items. More particularly, FR 2 658 034 relates, on the one hand, to an anti-adhesive and self-supporting membrane having the shape of a mould or a cavity plate, which is continuous, the surface of which in contact with the items of viennoiserie, pastries, biscuit products, is smooth and anti-adhesive, and which is flexible and resilient, i.e. is capable of deformation for the requirements of removing said items from the mould, and, on the other hand, a method for producing such a membrane.
According to the desired shape, this membrane is obtained by pressing and/or moulding a knitted fabric, preferably a double knitted fabric, i.e. a textile formed from two interlaced knitted fabrics, of glass or ceramic threads or similar materials, previously impregnated with an anti-adhesive silicone elastomer hardened by vulcanization. The membrane, which has thus acquired its final shape, is then treated on its inner surface by spraying with a silicone elastomer or dipping into a silicone solution, resulting in a flexible coating, having very strong anti-adhesive properties, and a smooth contact surface.
Preferably, the method for producing such a membrane comprises the following steps:                thorough impregnation of a knitted fabric of threads as stated above with a silicone suitable for contact with food and ensuring the self-supporting structure of the whole after vulcanization;        removal of the excess silicone so as to obtain an even, uniform and preferably aerated structure;        shaping or moulding of the silicone-impregnated knitted fabric by pressing so as to obtain the desired mould or plate with the desired cavities;        vulcanizing the preformed silicone-impregnated knitted fabric; and        spraying the face turned towards the desired cavity or cavities of the full membrane thus obtained, with a silicone solution of lesser hardness, having high covering and anti-adhesive properties, or        dipping the thus-obtained membrane into a bath of silicone in order to obtain a smooth silicone surface on the side of the knitted mesh that is turned towards the cavity or cavities.        
Generally, at least two silicone coatings of the knitted web are always carried out, the first coating being carried out with a silicone ensuring the rigidity of the material so that it is self-supporting, the last being carried out with a flexible silicone, having very high anti-adhesive properties and, preferably, with a very high elongation coefficient.
A thus-produced membrane can be formed so as to constitute a single cylindrical mould, having a round, square or rectangular cross section, which can be used domestically or professionally for freezing or baking by heat or microwaves of pastries or culinary preparations, however varied these may be, the membrane also being capable of forming several round, square, rectangular or truncated moulds, with or without channels, and then being called a “cavity plate”.
A further subject of FR 2 774 554 is a flexible and self-supporting mould or cavity plate, having an anti-adhesive inner surface suitable for contact with food, for the moulding and baking of bread dough or similar, and comprising a cloth defining a support impregnated with at least one resin of the crosslinked polysiloxane type, said cloth being thermoformed and provided with at least one suitable anti-adhesive coating layer, in particular based on a rubber or silicone elastomer suitable for contact with food, at least on its surface that is intended for contact with food.
As an intermediate product for the production of thermoformed articles, in particular moulds or cavity plates as defined above, a subject of this patent document is also a pre-impregnated cloth, constituted by a cloth impregnated with at least one polysiloxane resin that is potentially hot-polymerizable and thermoformable, the term “cloth” being used as a generic term encompassing all textile surfaces or textile constructions and felts, the cloths being capable of being constituted by any textile fibre or textile thread, and comprising flexible woven fabrics, whether woven, knitted, felted (or cloths produced of non-woven fabrics), needle-punched, stitched or produced by another production method. With respect to the fibres, these can be glass fibres, carbon fibres, aromatic polyamide fibres, ceramic fibres, or also a mixture thereof; other fibres can be envisaged insofar as they can withstand a temperature of the order of 300° C. WO 03/066328 relates to composite articles for cooking, comprising a thermoplastic organic polymer cloth impregnated or coated with a heat-resistant polymer and polymerized or crosslinked, and more particularly dough moulds that can be used for containing dough pieces during both the fermenting and the baking phases, the composite structure of the articles having sufficient rigidity for it to be self-supporting and being dimensionally stable up to a temperature of at least approximately 195° C. Preferably, the thermoplastic organic polymer is polyester and the heat-resistant crosslinked polymer is a silicone rubber. Generally, in addition to polyesters, suitable thermoplastic polymers comprise polyamides and polyimides, in particular in the form of fibres, and the textile cloth or structure constituting the supporting framework of the composite article can be a woven fabric, a non-woven or a knitted fabric, a knitted structure of polyester fibres or textured filaments or threads being preferred.
Such a composite structure has sufficient rigidity to be self-supporting and is dimensionally stable up to temperatures of the order of 175 to 195° C.
Composite articles according to the preferred form described in WO 03/066328 have been produced and marketed.
As mentioned in WO 03/066328, these composite articles have the main drawback of not withstanding baking temperatures higher than approximately 175° C. or 195° C., which severely limits their field of use, and therefore their benefit for industrial, semi-industrial and traditional use and even use by the general public.
By contrast, the composite membranes defining cavity moulds produced according to EP 0 235 037 and FR 2 658 034, with mainly glass fibre frameworks, allow baking up to temperatures of the order of 300° C., while providing users with the expected services in terms of anti-adhesivity, easy removal from the mould, flexibility and ease of use, with no return of the mould to the manufacturer due to destruction of the bond between the silicone of the matrix and the glass fibres of the reinforcing framework of the composite membrane.
However, the glass fibre framework of these membranes can exhibit, under intensive use, phenomena of fibres breaking at the locations where the mechanical stresses are greatest, as a result of shearing of the glass fibre threads or filaments, constituting, for example, the mesh of a reinforcing knitted fabric, especially if these moulds are also used in phases of freezing or deep-freezing of the food products contained in the moulds, as the glass fibres become brittle at temperatures of −30° C. to −40° C. As a result, tearing of the membrane can occur, making the mould unusable. Moreover, the more complex the shape of the cellular membrane, the greater the stress undergone by the glass fibre framework on shaping this membrane, owing to the number and/or the shapes of the cells that are themselves complex. Finally, the variation in the quality and/or the sizing characteristics of the glass fibres provided for the production of the cavity moulds can result in limitations in the performance of such moulds.
As far as the Applicant is aware, no flexible mould according to the specific teaching of FR 2 774 554 has been produced and marketed, in particular with a framework constituted by a mixture of glass, carbon, aromatic polyamide and ceramic fibres.